Question

Calculate the dosages as indicated. Use the labels where provided. A client has an order for inamrinone (previously called amrinone) \(250 \mathrm{mg}\) in \(250 \mathrm{~mL}\) \(0.9 \% \mathrm{NS}\) at \(3 \mathrm{mcg} / \mathrm{kg} / \mathrm{min} .\) Client's weight is \(59.1 \mathrm{~kg} .\) Determine the flow rate in \(\mathrm{mL} / \mathrm{hr}\).

Short answer

The flow rate should be approximately 10.64 mL/hr.

Step-by-step solution

Understanding the Dosage Formula

The given dosage is 3 mcg/kg/min, where mcg stands for micrograms. Since the weight is provided in kilograms and the time frame in minutes, this will be the basis for further calculations.

Convert Dose to mg

The order is given in micrograms but needs to be in milligrams for our ease of calculation with the provided vial concentration. Since 1 mg = 1000 mcg, the ordered dosage is: 3 mcg/kg/min = 0.003 mg/kg/min.

Calculate Total Dose per Minute

Multiply the client’s weight by the dosage per kilogram per minute: \[ 0.003 \, \text{mg/kg/min} \times 59.1 \, \text{kg} = 0.1773 \, \text{mg/min}. \]

Adjust Dosage for the Concentration

The solution has 250 mg of inamrinone in 250 mL NS, resulting in a concentration of 1 mg/mL. Therefore, 0.1773 mg corresponds to 0.1773 mL since the ratio is 1:1.

Convert Flow Rate to mL/hr

Since the calculated dosage is per minute, convert it to per hour: \[ 0.1773 \, \text{mL/min} \times 60 \, \text{min/hr} = 10.638 \, \text{mL/hr}. \]

Round Off the Flow Rate

Round 10.638 mL/hr to a practical value for infusion settings. The flow rate is approximately 10.64 mL/hr when rounded to two decimal places.

Key concepts

Micrograms to Milligrams Conversion

Many medication dosages are measured in micrograms (mcg), but sometimes, for ease of calculation or to match supplied vial information, you may need to convert these to milligrams (mg). This conversion is crucial in medical settings to ensure accurate dosing and prevent medication errors. Here's a simple guide to converting micrograms to milligrams.

• Understand the conversion factor: 1 mg equals 1000 mcg.
• To convert micrograms to milligrams, divide the number of micrograms by 1000.
• For example, if you have a dosage of 3000 mcg, you would convert it to milligrams as follows: \( 3000 \text{ mcg} \div 1000 = 3 \text{ mg} \).

This calculation ensures that you can apply the dosage correctly using available medication concentrations, showing practical understanding in preparing and administering medications.

Flow Rate Calculation

Flow rate calculation is a fundamental skill for healthcare providers, particularly in scenarios involving intravenous drug administration. It simply refers to the rate at which a medication solution needs to be delivered to a patient over a specified period of time. Let's walk through its calculation step-by-step.

• First, determine the dosage required per minute: This involves the medication amount needed according to the patient's weight and the prescription."
• Convert this dosage to the volume needed per minute based on the solution's concentration."
• To find the hourly flow rate, multiply the per-minute volume by 60."

Returning to our example, start with the per-minute dosage of 0.1773 mg. Since the concentration is 1 mg/mL (as seen with 250 mg in 250 mL), the volume equals 0.1773 mL per minute. To convert this to an hourly rate, multiply by 60 to get approximately 10.64 mL/hr.
Understanding how to calculate flow rates ensures safe and efficient drug delivery.

Drug Concentration

Drug concentration involves understanding how much of a drug is present within a given volume of solution. This concept is vital as it directly impacts how much of a medication a patient receives with each milliliter infused. Let’s break down this concept clearly.

• The concentration of a drug is typically noted as how many milligrams of the active ingredient are present per milliliter of solution (mg/mL).
• In the exercise, the solution provided is 250 mg of inamrinone in 250 mL of normal saline, indicating a concentration of 1 mg/mL.
• This direct ratio makes it straightforward to determine how much of the solution must be delivered to administer a specified dose of the active drug.

Grasping drug concentration is essential for adjusting doses accurately, ensuring that patients receive the intended amount of medication without underdosing or overdosing.